The present invention relates to an EUV light source that emits EUV light, an EUV exposure apparatus that uses the EUV light source, and a method for manufacturing an electronic device with the EUV exposure apparatus.
Due to the recent trend in miniaturization of semiconductor integrated circuits, an EUV exposure apparatus that uses EUV (Extreme Ultraviolet) light having a wavelength of about 5 to 50 nm has been proposed to improve the resolution of an optical system, which is restricted by the diffraction limit of the light.
In such an EUV exposure apparatus, the use of an EUV light source capable of supplying EUV light at a high output power is required for high throughput. In particular, as a high output power EUV light source, a light source that plasmatizes a target material including Sn and radiates EUV light has been discussed (for example, refer to “Laser Generation Plasma Light Source”, Toshinao Tomie; The Journal of the Japan Society of Plasma Science and Nuclear Fusion Research Vol. 79, No. 3 (2003), pp. 234-239.).
When using a metal such as Sn as the target material, a high density solid target would generate plasma with a high ion density. This increases self-absorption of the EUV light and lowers the output power. On the other hand, it is known that when using a low density solid target, light emission components are reduced at a wavelength band outside the peak of the emission spectrum. This improves the conversion efficiency to the useful EUV light wavelength.